1. Field of the Invention
This invention relates to distance measuring apparatus of the type having a rotatable wheel and, more particularly, to a distance measuring apparatus having a scraper assembly with a scraping edge for intercepting foreign matter adhered to the wheel as the wheel is rotated.
2. Background Art
Distance measuring apparatus utilizing rotatable wheels are well known in the art. In a typical construction, a frame supports a wheel for rotation around an axis. The frame has an associated handle which can be grasped to manipulate the frame and thereby roll the wheel against a surface upon which a distance measurement is to be taken. A counter is activated as the wheel is rotated and converts rotation to a distance measurement, which is digitally or mechanically displayed. This conversion is based upon the diameter for the wheel. That is, each wheel rotation is correlated to a distance traversed by the wheel which is equal to the wheel circumference.
Wheeled distance measuring apparatus are used in a wide range of environments. These apparatus are commonly used by the construction industry on sites at which terrain and conditions may be quite harsh. It is common for those utilizing wheeled distance measuring apparatus to encounter muddy conditions that may be aggravated when there is precipitation.
As a result of using wheeled distance measuring apparatus in the above-described environments, there is a tendency of foreign matter, such as chunks of earth, or the like, to adhere to the wheel. The adhered foreign matter has a number of undesirable effects. First, foreign matter at discrete locations on the wheel periphery may preclude smooth rolling of the wheel over the underlying terrain. A significant buildup may ultimately produce interference between the wheel and other parts of the apparatus, thereby impairing operation. To eliminate this latter problem, the user may be required to manually scrape the foreign matter off of the wheel. To accomplish this, the user may have to interrupt the measuring process and use a separate utensil to scrape the wheel periphery. Aside from the obvious inconvenience, this process may result in a compromise of the accuracy of the measurements by reason of not resuming the measuring process at the precise point at which it was interrupted.
Most significantly, the accumulation of foreign matter upon the wheel increases the effective circumference of the outer surface which rolls against the underlying surface upon which a measurement is taken. Foreign matter may progressively accumulate on the wheel and go virtually undetected by the user. Eventually, the foreign matter may accumulate to the point that an appreciable change in the effective diameter of the wheel results. Over long distances, a deviation from true measurement may result that is significant.
The industry continues to seek out new designs for distance measuring apparatus which are capable of taking accurate distance measurements even on rough and potentially wet and muddy terrain.